Sustainable dairy production systems: factors affecting heifer survival, lifetime productivity and replacement rateTools Botting, Philippa (2017) Sustainable dairy production systems: factors affecting heifer survival, lifetime productivity and replacement rate. MRes thesis, University of Nottingham.
AbstractGlobal per capita consumption of dairy products is set to rise 12.5% by 2025. Heifers make significant contributions to farm profitability and increasing the efficiency of heifer rearing can lead to significant improvements in whole farm productivity. This study used historical data to evaluate the influence of morbidity in the rearing period on age (AFC) and live weight at first calving (LWFC) and the effects of these parameters on lifetime performance. Records of 1,188 Holstein heifers born between 2006 and 2017 on a UK dairy farm were analysed for morbidity, mortality, AFC, LWFC, milk yield in first lactation, longevity and lifetime productivity. Overall rearing period mortality rate was 18.8%, with greater neonatal mortality observed in winter. Heifers that received 5 or more clinical treatments for morbidity exhibited a significantly greater AFC than heifers that received none. Mean AFC was 759d and mean LWFC 571 kg; only 12.1% of animals met the target AFC and LWFC and only 4.9% the target AFC and mature weight. Reduced milk yields were seen in animals calving at <700 days and <550 kg, however above these weight and age categories, no significant increases in yield were observed. Analysis of AFC and LWFC in combination revealed LWFC was a greater predictor of first lactation milk production. Proportion of life spent productive and lifetime DIM were greatest in heifers calving for the first time at <759d and <500 kg, who spent on average 50% of their life in a productive state compared to just 33% in the highest weight category. In summary, optimum lifetime performance was achieved with an AFC of 701 to 759 days, a LWFC of 551 to 600 kg and a proportion of mature weight of 79 to 81%, with these heifers ensuring a balance between productive life and milk yield in first lactation.
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